Propellent powder



an improved astatic smokeless powder.

United States Patent Qfiice 2,930,393 Patented Nov. 15, 1960 PROPELLENT POWDER Claude J. Barr, Herrin, Ill., assignor to Olin Mathieson Chemical Corporation, East Alton, 111., a corporation of Virginia No Drawing. Filed Feb. 5, 1958, Ser. No. 713,307

4 Claims. '(Cl. 52.5)

This invention relates generally to explosives and more particularly to propellent powder grains.

Smokeless powder grains are normally provided with a base of nitrocellulose or other gelatinizable polynitro compounds. Such materials readily accumulate static charges. When a static charge is built up on the powder grains, the grains tend to adhere to one another as well as to containers and other equipment used in their processing. In addition, static build-up also creates a definite hazard, for visible sparks can often be drawn from containers of powder that has not been treated to render it relatively astatic.

The electrostatic properties of propellent powder are normally corrected to prevent static build-up by providing the powder grains with a glazing of graphite. This is accomplished by tumbling the powder grains with graphite for about 2 hours to insure that each grain is completely coated. Such a process can be readily utilized in normal manufacturing operations when the powder grains have an average particle size greater than about 0.010 inch. However, the conventional graphite glazing operation cannot be applied to propellent powder grains having a substantially smaller particle size, as is required for certain plastisol processes. In fact, it has been found that when finely divided powder is tumbled with graphite for periods up to 24 hours the coating is uneven and, at best, only partially satisfactory. Also, because of the relatively large surface area of the finely divided powder, it is necessary to increase the amount of graphite used beyond the limits permitting both proper ballistic functioning and the consolidation of the fine powder grains into a rocket grain or other thick web propellant.

It is, therefore, an object of this invention to provide a smokeless powder overcoming the disadvantages of the prior art. Another object of this invention is to provide It is a more specific object of this invention to provide astatic smokeless powder grains devoid of a surface coating of graphite.

In accordance with this invention, generally stated, these and other objects are accomplished by providing propellen-t powder grains containing a strongly polar, long chain, antistatic agent. More specifically, this invention contemplates smokeless powder grains containing as antistatic agents polyethyleneimines, amine salts of long chain alkyl phosphates, alkyl pyridinium halides, diguanidine salts of esters of sulfo-succinic acid with long chain aliphatic acids, ketoaminoalkyl quaternary ammonium salts, guanylurea salts of monoalkyl esters of sulfuric acid, long chain fatty acid esters of hexitol anhydrides, or hydroxy-polyalkylene esters of hexitol anhydrides. These antistatic agents can be applied to the powder as a coating or can be incorporated throughout the body of the grains. In either case, the presence of such antistatic agents prevents static build-up on powder grains and renders them free flowing and safe to handle regardless of their particle size. Such agents are equally effective with single base powders consisting essentially of forming substance such as guanidine,

nitrocellulose or other gelatinizable explosive material and with double base powders having, for example, a nitrocellulose-nitroglycerin base. While various proportions of the antistatic agent can be added to the powder, it has been found necessary to maintain the content of the agents below about 1% by weight of the powder. Greater amounts of the agents tend to exhibit a strong deterrent eifect upon the combustion kinetics of the grains, giving them undesirable ballistic characteristics. The powder grains can be coated with the antistatic agent by suspending the powder grains in a non-solvent medium containing a dispersion of the antistatic agent or by dipping them into a solution or dispersion of the agent. When his desired to incorporate the agent directly into the grains rather than merely coat the surfaces of the grains, the antistatic agent or a solution thereof can be incorporated into the smokeless powder base prior to the grain forming operation.

The polyethyleneimines contemplated in accordance with this invention have average molecular weights between about 300 and about 3,000. Those having molecular Weights in the neighborhood of about 800 are generally preferred. The invention also contemplates derivatives of such polyamines containing an alkyl group, a hydroxy alkyl group, an amino alkyl group, or high fatty acyl and acimido groups attached to one or more of the nitrogen atoms. The amine salts of long chain alkyl phosphates contemplated may be represented by the general formula chain aliphatic acids are best represented by the following general formulae:

In these formulae, R and R represent long chain aliphatic groups containing from 9 to 17 carbon atoms, R is an alkylene or hydroxyalkylene radical containing from 2 to 5 carbon atoms, and Gn represents a cationic saltthe lower alkylguamdines, the alkylolguanidines, guanylurea, the biguanidines, or the phenolbiguanidines.

The ketoaminoalkyl quaternary ammonium salts found suitable for antistatic agents in accordance with this invention are represented by the following formula:

. V V R!!! wherein R is a long chain'aliphatie radical containing at least 7 carbon atoms, R and R" are alkyl radicals containing from 1 to carbon atoms, R may be an alkyl or alkenyl radical containing up to 5 carbon atoms, and Y represents an anion such as halide, sulfate, phosphate, borate, nitrate, or the like.

The guanylurea salts of mono-alkyl esters of sulfuric acid that have been found most suitable for use in achieving the benefits of this invention have been those containing at least 12 and not more than 18 carbon atoms. The long chain fatty acid esters of hexitol anhydrides and the hydroxypolyethylene ethers thereof contemplated in accordance with this invention include such esters having between 12 and 18 carbon atoms in their alkyl radicals. Sorbitan monolaurate and sorbitan monos'tearate polyoxyethylene ether are representative of this type of compound.

While various theories have been proposed in efforts to explain the manner in which these antistatic agents prevent the build-up of static on smokeless powder grains, the mechanism involved is not completely understood. In any event, when such agents are present in powder in proportions up to about 1%, it has been found that the powder exhibits adequate astaticity for processing.

In order to illustrate the advantages of this invention, a batch of powder of the general type described in Us. Patent 2,160,626 issued to Schaefer was prepared. This was a single base, generally spherical powder having an average particle size between about 0.0059 and 0.0098 inch, and consisted predominantly of nitrocellulose containing approximately 1% 2-nitrodiphenylamine as a stabilizer. This powder was then treated with the antistatic agents of the present invention. Untreated powder of this type was exceedingly electrostatic. This caused the powder to cluster and to adhere to the walls of containers and apparatus. Thus, this powder was diflicult to handle and, in addition, it generated sparks very readily. In the following examples, all proportions are expressed in parts by weight unless otherwise designated.

Example I Polyethyleneimine was prepared by mixing one part of ethyleneimine with 3 parts of water and refluxing the mixture for about 20 hours. The resultant polymer had an average molecular weight of about 900 and was dissolved or suspended in 3 parts of water. This material was diluted to provide an aqueous solution containing about 2% of the polyethyleneimine.

Approximately 100 parts by weight of the powder described above were introduced into about 1000 parts of the 2% polyethyleneirnine solution at room temperature and the powder was maintained in this solution for about minutes. At the end of this time the powder was removed and dried. The resultant powder contained approximately 0.5% polyethyleneimine. This powder was free flowing and showed no tendency to accumulate a static charge even when tumbled in a conductive cylinder.

Example 11 About 100 parts by weight of the powder described above was suspended in approximately 500 parts of a 5% aqueous dispersion of the diethanolamine salt of dilauryl phosphate. The suspension was maintained at room temperature for about 15 minutes. The powder was then separated from the dispersion and dried. This powder was provided with a coating of the diethanolamine salt representing approximately 0.1% of the weight of the powder. Here again, the powder was free flowing and astatic.

Example III A 5% solution of lauryl pyridinium chloride in equal portions of ethyl alcohol and water was prepared. About 100 parts by weight of the powder was suspended in about 500 parts of this solution at room temperature for about 5 minutes, removed and dried. This powder contained approximately 0.05% of the chloride and was free flowing and showed no tendency to accumulate static charge.

Example IV An aqueous solution of mono-n-dodecyl diguanidine sulfosuccinate was prepared by reacting n-dodecyl alcohol with maleic anhydride to obtain a maleic monoester of n-dodecyl alcohol which was then reacted with guanidine sulfite. About 1,000 parts of a 5% solution of sulfosuccinate salt was maintained at a temperature of about 45 C. and parts of the smokeless powder added thereto. After about 5 minutes, the powder was removed and dried. By this treatment, the powder acquired a coating of the salt representing about 0.03% of the weight of the powder, and was free flowing and astatic.

Example V About 100 parts of the powder were added to about 1000 parts of a 10% aqueous solution of stearamidopropyldimethyl-beta-hydroxyethylammonium dihydrogen phosphate at room temperature. The powder was soaked in this solution for approximately 10 minutes, after which the solution was decanted and the powder dried. The resultant powder contained approximately 0.06% of the salt and showed no tendency to maintain or accumulate static charges.

Example VI A 1% dispersion of guanylurea octadecyl hydrogen sulfate was prepared by adding one part of the sulfate to 99 parts of water and heating to boiling, after which the dispersion was cooled to approximately 50 C. About 100 parts of the finely divided propellent powder was then suspended in about 1000 parts of this dispersion for about 10 minutes at 50 C. The powder was dried after separating it from the dispersion. Here again, the powder was astatic and free flowing.

Example VII About 100 parts of the powder described above was suspended in about 500 parts of a 1% aqueous disper: sion of sorbitan monolaurate at room temperature for about 5 minutes. The powder was then removed from the dispersion and dried. This powder, containing approximately 0.05% of the sorbitan monolaurate as a coating, was free flowing, and resistant to static accumulation.

Example VIII About 100 parts of nitrocellulose were dissolved in approximately 320 parts of ethyl acetate to form a nitrocellulose lacquer. After the lacquer was formed, approximately 0.10 part of lauryl pyridinium chloride were added thereto with mixing to insure that the lauryl pyridinium chloride was uniformly distributed throughout the lacquer. This lacquer was then added to about 800 parts of water containing approximately 1% dissolved sodium sulfate. The lacquer was broken down into small globules suspended in the water and the solvent removed from the suspended lacqu r particles to form spherical grains of powder in accordance with the process as generally described in 11.8. 2,160,626 issued to Schaefer. This powder contained approximately 0.06% lauryl pyridinium chloride, was free filowing and showed no tendency to accumulate static charges. By contrast, a powder prepared in accordance with the same process but not containing lauryl pyridinium chloride was exceedingly electrostatic and diflicult to handle.

While the above examples are directed to specific methods for the addition of the antistatic agents to the powder, it is to be understood that many modifications can be employed depending upon the manner in which the powder is prepared and also upon the particular antistatic agents used.

The antistatic agents of this invention can be advantageously utilized with smokeless powder grains having a base of nitrocellulose, nitrocellulose and accelerators, nitrocellulose and deterrents, nitrocellulose-nitroglycerin with deterrents as well as other similar gelatinizable polynitro compounds such as nitro starch and polyvinyl nitrate.

Many other changes in the invention will occur to those skilled in the art and can be used without departing from the spirit and scope of this invention, except as it is delineated by the appended claims.

What is claimed is:

1. A propellent powder consisting essentially of a pro pellent powder base selected from the group consisting of nitrocellulose, nitrocellulose-nitroglycerin, nitrostarch, and polyvinyl nitrate, and up to about 1 percent of an alkyl polar antistatic agent selected from the group consisting of polyethyleneimines, amine salts of long chain alkyl phosphates, alkyl pyridinium halides, diguanidine salts of esters of sulfosuccinic acids with long chain aliphatic alcohols, quaternary ammonium salts of long chain ketoaminoalkyl compounds, guanylurea salts of monoalkyl esters of sulfuric acid, long chain fatty acid esters and hydroxy-polyalkylene esters of hexitol anhydrides.

2. A propellent powder grain consisting essentially of a propellent powder base selected from the group consisting of nitrocellulose, nitrocellulose-nitroglycerin, nitrostarch, and polyvinyl nitrate, and up to about 1 percent of an alkyl polar antistatic agent selected from the group consisting of polyethyleneimines, amine salts of long chain alkyl phosphates, alkyl pyridinium halides, diguanidine salts of esters of sulfosuccinic acids with long chain aliphatic alcohols, quaternary ammonium salts of long chain ketoaminoalkyl compounds, guanylurea salts of monoalkyl esters of sulfuric acid, long chain fatty acid esters and hydroxy-polyalkylene esters of hexitol anhydrides.

3. A process for the manufacture of astatic propellent powder comprising adding to a propellent powder base selected from the group consisting of nitrocellulose, nitrocellulose-nitroglycerin, nitrostarch, and polyvinyl nitrate, up to about 1 percent of an alkyl polar antistatic agent selected from the group consisting of polyethyleneimines, amine salts of long chain alkyl phosphates, alkyl pyridinium halides, diguanidine salts of esters of sulfosuccinic acids with long chain aliphatic alcohols, quaternary ammonium salts of long chain ketoaminoalkyl compounds, guanylu-rea salts of mono-alkyl esters of sulfuric acid, long chain fatty acid esters and hydroxy-polyalkylene esters of hexitol anhydn'des, and subsequently graining the propellent powder base.

4. A process for the manufacture of astatic propellent powder comprising immersing propellent powder grains having a base selected from the group consisting of nitrocellulose, nitrocellulose-nitroglycerin, nitrostarch, and polyvinyl nitrate in a liquid aqueous medium which is a non-solvent for the grains and containing an alkyl polar anti-static agent selected from the group consisting of polyethyleneimines, amine salts of long chain alkyl phosphates, alkyl pyn'dinium halides, diguanidine salts of esters of sulfosuccin-ic acids with long chain aliphatic alcohols, quaternary ammonium salts of long chain ketoaminoalkyl compounds, guanylurea salts of mono-alkyl esters of sulfuric acid, long chain fatty acid esters and hydroxypolyalkylene esters of hexitol anhydrides, and thereafter draining and drying the grains.

No references cited. 

1. A PROPELLENT POWDER CONSISTING ESSENTIALLY OF A PROPELLENT POWDER BASE SELECTED FROM THE GROUP CONSISTING OF NITROCELLULOSE, NITROCELLULOSE-NITROGLYCERIN, NITROSTARCH, AND POLYVINYL NITRATE, AND UP TO ABOUT 1 PERCENT OF AN ALKYL POLAR ANTISTATIC AGENT SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENEIMINES, AMINE SALTS OF LONG CHAIN ALKYL PHOSPHATES, ALKYL PYRIDINIUM HALIDES, DIGUANIDINE SALTS OF ESTERS OF SULFOSUCCINIC ACIDS WITH LONG CHAIN ALIPHATIC ALCOHOLS, QUATERNARY AMMONIUM SALTS OF LONG CHAIN KETOAMINOALKYL COMPOUNDS, GUANYLUREA SALTS OF MONOALKYL ESTERS OF SULFURIC ACID, LONG CHAIN FATTY ACID ESTERS AND HYDROXY-POLYALKYLENE ESTERS OF HEXITOL ANHYDRIDES. 